DE 31 36 746 C2 discloses an electronic control unit pertaining to a device which can be influenced by control elements and by a sensor device. Dependent measured values are continually transmitted to the electronic control unit from the sensor device, e.g., the number of turns or the opening or closing speed of the adjustable device component or the pertaining servo motor, and these values are subjected to a sector-related evaluation.
Specifically, this means that there is no monitoring in the first sector ranging from the completely open to the approximately half-open status of the device. In a second sector which ranges from the approximately half-open to the almost completely closed status of the device, the previously mentioned monitoring is carried out which is directed at the safety aspect. This sector could of course be extended to include the former sector without additional circumstance, in the event that the same safety level were required for the first sector.
No monitoring takes place in a third (rather small) sector ranging from the almost completely closed status to the completely closed status of the device and pertaining to the arrival of the adjustable device component at the sealing arrangement provided at that location. This is due to the fact that no further danger to parts of the body can arise in this sector.
With a device designed in this manner, the problem arises that the servo motor or its rating must be conceived in such a way that the mechanical resistances are overcome which arise over the adjustment range, e.g., as the result of constructive design of the device or externally caused mechanical resistances. In consequence, this means that the servo motor must be designed with a much higher rating than is necessary for the need required for the greater part of the moving travel. As a result, however, the problem arises that limbs can be trapped with an irrelatively great power/travel ratio by the moving device.
DE 37 28 008 A1 makes known an actuating device for movable parts for closing and opening apertures in which it is possible to alter the number of turns of the servo motor, and consequently the speed of the movable parts. However, no reference can be derived from this to a position-related effect on the number of turns for the purpose of limiting the force exercised in the case of trapped objects. On the contrary, it is emphasized that the turning moment, i.e., the force is maintained even when the number of turns is reduced.